<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        let arr = [3,1,2]
        let max = arr[0]
        let min = arr[0]
        for (let i = 0; i < arr.length; i++) {
            if (max < arr[i + 1]) {
                max = arr[i + 1]
            }
            if (min > arr[i + 1]) {
                min = arr[i + 1]
            }
        }
        alert(`最大值是${max}`)
        alert(`最小值是${min}`)

    </script>
</body>

</html>